1. Field of the Invention
The present invention relates to a branched power transmission having a continuously variable transmission ratio.
2. Description of the Related Art
Transmissions having a continuously variable transmission ratio and that contain a speed change mechanism along with two pairs of conical disks around which a belt passes, are attracting more and more interest, not only because of the high level of driving comfort that they achieve, but also because of the possible wear reduction.
Known branched power transmission structures are characterized by the fact that at one limit of the transmission ratio of the branched power range, through the adjustability of the speed change mechanism, they impose only a slight load on the speed change mechanism. In that range the overall transmission ratio of the transmission is only slightly changed when the speed change mechanism transmission ratio is adjusted, whereas at the other limit of the branched power range the speed change mechanism basically transfers all of the power. In the latter range, in any event, the overall transmission ratio of the branched power transmission is heavily dependent on that of the speed change mechanism.
In the design of such transmissions, the “worst” operating point, at one edge of the transmission ratio range, which limits the moment and spread capacity attainable with branched power transmissions, must always be taken into account. In view of the high peak pressures and volume flows, the construction of a hydraulic system for the adjustment of the transmission ratio of the speed change mechanism, that is, in a continuously variable transmission, the adjustment of the spacings between the conical disks in the conical disk pairs becomes more difficult, and the construction of the conical disk pairs themselves is more expensive because of the higher contact and adjustment forces involved. For the design of the endless torque-transmitting means (for example, a plate-link chain) and the formation of the conical surfaces, the operating point with the greatest load is crucial.
An additional characteristic of known branched power transmissions involves their complex structure, with numerous mechanical connections between individual active transmission components, such as the speed change mechanism and the planetary transmission. In many cases, an intermediate shaft must transfer the torque from one side of the speed change mechanism to the other. Connected therewith is often the individual adjustment of numerous components in order to conform with a wide range of motor-vehicle- or engine-specific requirements.
The invention is based on the task of providing a solution for the problems set forth above.